using variables in regular expr replace

b888 has asked for the wisdom of the Perl Monks concerning the following question:

Gretting all.

I trued to use variables in s/// and met following problem: perl interpreter tries to use these variables' values as reg expessions. How can i ommit this?

In general algorythm looks like

my $line = "<a href=\"/{HOST}?action\">123</a>:</b><br>".
           "[img-smile \"58-41\" \":)\"]";
my $var1 = "<img src=\"1-2.gif\" alt=\"[---]\">";
(my $var2) = $line =~ /(\[img-smile [^]]+\])/;
$line =~ s/$var2/$var1/;
print $line;
[download]

And get Invalid [] range "8-4" in regex; marked by <-- HERE in m/[img-smile "58-4 <-- HERE 1..."

P.S. I can't use ' instead of " because of algorytm specific.

Comment on using variables in regular expr replace Download Code

Replies are listed 'Best First'.
Re: using variables in regular expr replace by Joost (Canon) on Dec 02, 2004 at 12:45 UTC
You can disable regex interpretation of a supplied variable by using \Q and \E: `$line =~ s/\Q$var2\E/$var1/;` [download] See perlre for more info. "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply] [d/l]
Re^2: using variables in regular expr replace by Fletch (Bishop) on Dec 02, 2004 at 12:57 UTC
And just to elaborate on why you need to do this, remember that `[]` indicates a character class inside a regular expression (i.e. `[a-c]` means any of the characters `a`, `b`, or `c`). Your `[img ... 8-4 ... ]` is being interpreted as a character class, and you've got an invalid range (the character `8` is "bigger" than `4` and hence the correct way to specify the range of characters would be `[4-8]`). At any rate you really should either escape the square brackets or use `\Q...\E` as shown above (and you should read `perldoc perlretut` and `perldoc perlre`).	[reply] [d/l] [select]
Re: using variables in regular expr replace by Eimi Metamorphoumai (Deacon) on Dec 02, 2004 at 12:53 UTC
Use `\Q` and `\E` `$line =~ s/\Q$var2\E/$var1/;` [download] (In this case you don't need the `\E` at the end, since it'll end at the end of the regexp anyway, but it's good to know if you do need it later.) Also, I'm not sure what you mean by "I can't use ' instead of " because of algorytm specific", but if you need to interpolate variables and still not have to quote quotes. `my $line = <<"HTML"; <a href="/{HOST}?action">123</a>:</b><br>[img-smile "58-41" ":)"] HTML chomp $line;` [download] Or you can use `qq` with just about any delimiter. `my $line = qq#<a href="/{HOST}?action">123</a>:</b><br>[img-smile "58- +41" ":)"]#;` [download]	[reply] [d/l] [select]
Re^2: using variables in regular expr replace by b888 (Beadle) on Dec 02, 2004 at 13:05 UTC
Thanks to all	[reply]


Think about Loose Coupling
	PerlMonks

using variables in regular expr replace

This is an archived low-energy page for bots and other anonmyous visitors. Please sign up if you are a human and want to interact.