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Regular expression foo

vijayneedshelp
New User

Jul 11, 2011, 11:42 PM

Post #1 of 3 (1454 views)

Regular expression foo	Can't Post

my $pattern = "href=[\'\"](\/deals\/[0-9]+[^\?]+)\?msdc_id=[0-9]+[\'\"]";
print "yay\n" if $content =~ /href=[\'\"](\/deals\/[0-9]+[^\?]+)\?msdc_id=[0-9]+[\'\"]/;

print "yay\n" if $content =~ /$pattern/;

It only prints one "yay". Why does putting a pattern in a string not yield a match in the second case?

vijayneedshelp
New User

Jul 12, 2011, 12:13 AM

Post #2 of 3 (1452 views)

Re: [vijayneedshelp] Regular expression foo [In reply to]	Can't Post

Oh wow, I think I figured it out!

When you put a pattern in a string and use it as a regular expression, you need to double escape certain things.

Like if I want a literal match to the ? character I can't do:

$pattern = "\?";

I should do:

$pattern = "\\?";

That stumped me for ages!

macareus
New User

Jul 12, 2011, 1:30 AM

Post #3 of 3 (1449 views)

Re: [vijayneedshelp] Regular expression foo [In reply to]	Can't Post

You might want to look into the qr{} operator.
It quotes and interpolates the pattern; that is,
without rescanning.

Consult 'man perlop', and search for qr.

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