Re: Possible Match Problem

#!/usr/bin/perl -w
use strict;

my $str1 = "Hi(";
my $str2 = "hi";

if ($str2 =~ /\Q$str1\E/) #\Q...\E means like qr
                           #don't interpret characters
                           #like '(' within $str1
                           #use them verbatim
{
    print "Match: Yes\n";
}
else
{
    print "Match: No\n";
}
#prints Match: No


$str2 = "hI(";
if ($str2 =~ /\Q$str1\E/i) #/i means case insensitive
{
    print "Match: Yes\n";
}
else
{
    print "Match: No\n";
}
#prints Match: Yes
[download]

Basically if you want to match upon string where one or more characters would mean something to a Perl regex, you need to say that: "I don't want these special characters to count, i.e. mean something in a regex sense" - otherwise when Perl interpolates that string, those characters "will count". There are a couple of ways to say "please use all these characters verbatim", I showed one of these. ~~qr is another.~~

Comment on Re: Possible Match Problem Download Code

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Re^2: Possible Match Problem by AnomalousMonk (Archbishop) on Jan 19, 2012 at 06:05 UTC
... a couple of ways to ... use all these characters verbatim ... qr is another. In no way will `qr` use any metacharacters verbatim unless specifically 'told' to do so, e.g., by a `\Q ... \E` escape sequence. `>perl -wMstrict -le "my $s = 'hi('; my $rx = qr{$s}; " Unmatched ( in regex; marked by <-- HERE in m/hi( <-- HERE / at ...` [download] Update: See `qr` in the Regexp Quote Like Operators section of perlop, also see section on 'escape sequences' (for `\Q`) in Quote and Quote like Operators, also in perlop.	[reply] [d/l] [select]
Re^3: Possible Match Problem by Marshall (Canon) on Jan 19, 2012 at 08:30 UTC
correct. qr is better used for other things. my example was with \Q...\E, so I'll leave it at that.	[reply]
Re^4: Possible Match Problem by AnomalousMonk (Archbishop) on Jan 19, 2012 at 16:07 UTC
`if ($str2 =~ /\Q$str1\E/) #\Q...\E means like qr #don't interpret characters #like '(' within $str1 #use them verbatim` [download] To avoid misunderstanding, you might also consider removing "`like qr`" from the foregoing comment, or possibly changing to something like "`means,``as when used in qr, to avoid interpreting` `characters like ...`".	[reply] [d/l] [select]