RegEx Problem

[Jerry Baker]

Special characters inside of variables cannot be escaped, but Perl tries
to use them in a RegEx. Try this example program to see what I mean:

-----PROGRAM-----
#!/usr/bin/perl

$test = "This + test";
$test2 = "+";
if($test =~ /^This $test2 test$/) {
print "WORKS!!!";
}
else {
print "DOESN'T WORK";
}
-----PROGRAM-----

The result will always be "DOESN"T WORK". The same result will occur if
you change $test2 = "\+".

To verify that the program isn't at fault, the following always returns
"WORKS!!!":

-----PROGRAM-----
#!/usr/bin/perl

$test = "This + test";
if($test =~ /^This \+ test$/) {
print "WORKS!!!";
}
else {
print "DOESN'T WORK";
}
-----PROGRAM-----

How can I tell Perl to ignore "special" characters in a variable when
performing a RegExp comparison?

Thanks.

 

[Jerry Baker]

How can I tell Perl to ignore "special" characters in a variable when
performing a RegExp comparison?

The answer is \Q and \E.

-----PROGRAM-----
#!/usr/bin/perl

$test = "This + test";
$test2 = "+";
if($test =~ /^This \Q$test2\E test$/) {
print "WORKS!!!";
}
else {
print "DOESN'T WORK";
}
-----PROGRAM-----