use strict;
my $str = '{{Infobox xyz
|aaa= Xyz {{foo| {{A NESTED TEMPLATE}}}}
|bbb= [[Xyz]]
|ccc=[[File:xyz.jpg|thumb|Xyz.]]
|ddd= {{lang|en|xyz}}
}}
[[File:abc.jpg|thumb|Abc.]]';
my $regex = qr/(\{\{Infobox(?:[^{}]|\{\{(?:[^{}]|\{\{[^{}]*\}\})*\}\})*)\[\[ *(?:image|fi(?:le|chier)) *: *([^\|\]]*)[^\]]*\]\]/mip;
my $subst = '$1$2';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html