The $ in the regex needs to be escaped (like this: s/ \$VAR1/ my %hash /) so Perl doesn't go looking for a variable named $VAR1 and complain when it can't find it.

Also, you have a subtle error in your code. The line if ($line = ~s/ \$VAR1/ my %hash /) is actually performing the search and replace on the default variable $_ (which hasn't been set to anything), taking the bitwise negation of the result (the number of replacements made, most likely zero) and assigning that result to the $line variable, which will most likely be true and execute the if block. The code should be like this:

...
if ( $line =~ s/ \$VAR1/ my %hash / ) {
    ...
}
...

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In any case, this won't change your input file. You would need to write out to a new file after the search and replace.

A better way to do this is to specify the name of the variable when you dump your data structure using the $Data::Dumper::Varname variable, eg:

my %hash = (...);
$Data::Dumper::Varname = 'hash';
print Dumper(\%hash);

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An alternative is to use the object-oriented interface. You can specify your own names for your data structures, eg:

my %hash = (...);
print Data::Dumper->Dump( [\%hash], ['hash'] );

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See the docs for Data::Dumper for more details.

As an aside, you may want to consider dumping your data in a format such as XML or JSON, instead of as a Perl data structure.

Update: Minor clarifications re syntax.

In reply to Re: trouble with substitution by kejohm
in thread trouble with substitution by Interzona

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