pattern matching with substring containing special character

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hello monks!
I have a question:
Say you have the strings:

$a="ABCDABCDXBCDABCXABCDXXCDABXD";
$b="ABCDABCDABCDABCDABCDABCDABCDABCDABCDABCD";
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If in $a there were no X's, then with a pattern match you would say that $b includes $a. I need to write a pattern match to "ignore" other characters in $a if they are X, but DO NOT erase them. What I mean is that, in the position of X in $a, you could have A, B, C or D, does not matter. I tried the following but did not work:

$a="ABCDABCDXBCDABCXABCDXXCDABXD";
$b="ABCDABCDABCDABCDABCDABCDABCDABCDABCDABCD";

@split_initial=split(//, $a);
for ($i=0; $i<=$#split_initial; $i++)
{
    if($split_initial[$i] ne 'A' && $split_initial[$i] ne 'B' && $spli
+t_initial[$i] ne 'C' && $split_initial[$i] ne 'D')
    {
        $split_initial[$i]="*";
    }
    $seq_final=join('', @split_initial);
}

if ($b=~/$seq_final/) {print "OK\n";}
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I somehow try to insert artificially, the wildcharacter * in $a, so as to "ignore" what's in position of X (because it can be anything between A,B,C or D -it doesn't matter which one) when it searches $b for the presence of $a..
How can I write this pattern match correctly?

Comment on pattern matching with substring containing special character Select or Download Code

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Re: pattern matching with substring containing special character by GrandFather (Saint) on Mar 03, 2011 at 01:18 UTC
Replace the Xs with a character class match `[ABCD]` then use the resulting string as the match string: `use strict; use warnings; my $match = "ABCDABCDXBCDABCXABCDXXCDABXD"; my $str = "ABCDABCDABCDABCDABCDABCDABCDABCDABCDABCD"; $match =~ s/x/[abcd]/ig; print "Matched $1\n" if $str =~ /($match)/i;` [download] Prints: `Matched ABCDABCDABCDABCDABCDABCDABCD` [download] True laziness is hard work	[reply] [d/l] [select]
Re^2: pattern matching with substring containing special character by Anonymous Monk on Mar 03, 2011 at 01:36 UTC
Oh yes, great, I accidentally wrote "*" instead of "." as you pointed out... GrandFather, thanks also for your recommendation, good to learning new tricks!	[reply]
Re: pattern matching with substring containing special character by roboticus (Chancellor) on Mar 03, 2011 at 01:15 UTC
Try using a regex, by replacing your 'X' with '.', you can easily check if they match, something like (untested): `my $t="ABCDABCDXBCDABCXABCDXXCDABXD"; $t =~ s/X/./g; my $u="ABCDABCDABCDABCDABCDABCDABCDABCDABCDABCD"; if ($u =~/$t/) { print "match found\n"; }` [download] ...roboticus When your only tool is a hammer, all problems look like your thumb.	[reply] [d/l]