in reply to Re^4: regex basics
in thread regex basics

These are not the same: 
!$_ /;\s+/
!/\#\s+/

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In fact, when you want to mention the thing to be matched, you must use the binding operator: 

!( $_ =~ /;\s+/);
# or
$_ !~ /;\s+/;

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Update: Precedence fixed. Thanks AnomalousMonk.

لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

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Re^6: regex basics
by AnomalousMonk (Archbishop) on Feb 02, 2015 at 19:13 UTC
    ! $_ =~ /;\s+/;

    Because of the high precedence of the  ! (logical-not) operator versus  =~ (see perlop), the regex actually matches against either  '' (the empty string) or '1'. 

    c:\@Work\Perl>perl -wMstrict -MO=Deparse,-p -le
"! $_ =~ /;\s+/;
"
BEGIN { $^W = 1; }
BEGIN { $/ = "\n"; $\ = "\n"; }
use strict 'refs';
((!$_) =~ /;\s+/);
-e syntax OK

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    These are equivalent: 
    ! ($_ =~ /;\s+/);
# or
$_ !~ /;\s+/;

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    Give a man a fish:  <%-(-(-(-<

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Re^6: regex basics
by Anonymous Monk on Feb 04, 2015 at 07:18 UTC

    Understood.

    =~ means match and !~ means no match.

    This should work:

    #!/usr/bin/env perl
use strict;
use warnings;
my $iniprod = 'php.ini-production';
my $ininocm = 'php.ini-nocomments';
open my $IN,  '<', $iniprod
   or die "Could not open $iniprod for reading: $!";
my $text;
while (<$IN>) {
   if ($_ !~ /;\s+/) {
      $text .= $_;
   }
}
close $IN
   or die "Error closing $iniprod: $!";
# remove blank lines
$text =~ s{\n{2,}}{\n}gm;
open my $OUT, '>', $ininocm
   or die "Could not open $ininocm for writing: $!";
print $OUT $text;
close $OUT or die "Error closing $ininocm: $!";

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