Re: using variables in regular expr replace

[Joost]

You can disable regex interpretation of a supplied variable by using \Q and \E:

$line =~ s/\Q$var2\E/$var1/;

See perlre for more info.

[Fletch]

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).