Use splatting.
$CurlArgument = '-u', '[email protected]:yyyy',
'-X', 'POST',
'https://xxx.bitbucket.org/1.0/repositories/abcd/efg/pull-requests/2229/comments',
'--data', 'content=success'
$CURLEXE = 'C:\Program Files\Git\mingw64\bin\curl.exe'
& $CURLEXE @CurlArgument