What is the meaning of in Perl

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What is the meaning of    in Perl

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All Perl s  special variables  are listed in the perlvar documentation page

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The question was what    means in Perl  The answer to that question is that  insofar as    means it in Perl     similarly means they   No one seems to have mentioned this critical aspect of its meaning     as well as theirs   They   re consequently both  used as pronouns  or sometimes as topicalizers    They typically have nominal antecedents  although not always

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Usually  you expand the parameters passed to a sub using the    variable   sub test    my   a   b   c                   call the test sub with the parameters test  alice    bob    charlie      That s the way claimed to be correct by perlcritic

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Never try to edit to    variable     They must be not touched   Or you  get some unsuspected effect  For example     my  size 1234  sub sub1       0  500    sub1  size    Before call sub1  size contain 1234  But after 500     So you Don t edit this value    You may pass two or more values and change them in subroutine and all of them will be changed  I ve never seen this effect described  Programs I ve seen also leave    array readonly  And only that you may safely pass variable don t changed internal subroutine You must always do that   sub sub2    my  m                assign    to local subroutine procedure variables and next worked with them  Also in some deep recursive algorithms that returun array you may use this approach to reduce memory used for local vars  Only if return    array the same

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Also if a function returns an array  but the function is called without assigning its returned data to any variable like below  Here split   is called  but it is not assigned to any variable  We can access its returned data later through       str    Mr Bond Chewbaaka Spider-Man   split        str    print    0      Mr Bond    This will split the string  str and set the array

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is used for an array   In a subroutine or when you call a function in Perl  you may pass the parameter list  In that case     is can be used to pass the parameter list to the function   sub Average         Get total number of arguments passed       n   scalar           sum   0       foreach  item                  foreach is like for loop    It will access every           array element by an iterator          sum     item              average    sum    n       print  Average for the given numbers   average n       Function call  Average 10  20  30     If you observe the above code  see the foreach  item     line    Here it passes the input parameter

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First hit of a search for perl    says this         is the list of incoming parameters to a sub    It also has a longer and more detailed explanation of the same

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You can also use shift for individual variables in most cases    var1   shift    This is a topic in which you should research further as Perl has a number of interesting ways of accessing outside information inside your sub routine

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perldoc perlvar is the first place to check for any special-named Perl variable info    Quoting          Within a subroutine the array    contains the parameters passed to that subroutine    More details can be found in perldoc perlsub  Perl subroutines  linked from the perlvar      Any arguments passed in show up in the   array            Therefore  if you called a function with two arguments  those   would be stored in    0  and    1        The array    is a local array  but its   elements are aliases for the actual scalar parameters     In particular  if   an element    0  is updated  the   corresponding argument is updated  or   an error occurs if it is not   updatable         If an argument is an array   or hash element which did not exist   when the function was called  that   element is created only when  and if    it is modified or a reference to it is   taken   Some earlier versions of Perl   created the element whether or not the   element was assigned to   Assigning to   the whole array    removes that   aliasing  and does not update any   arguments

[perl] What is the meaning of @_ in Perl?

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