use strict;
my $str = '<input class="scf-composer-msg" type="text" class="scf-js-userfilter" data-field-type="userdropdown" name="composedFor" placeholder="{{#if properties.composedFor}}{{i18n "Composed for "}}
{{author.name}}{{else}}{{i18n "Compose On Behalf of a User"}}{{/if}}" data-attrib="composedFor" /> ';
my $regex = qr/({{i18n .*?}})/p;
my $subst = '$';
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