use strict;
my $str = 'Right (99.99руб.) OR Left with space (руб. 99.99) OR Right with space (99.99 руб.) OR Left (руб.99.99)';
my $regex = qr/руб\.\ ?(\d[\d.]+)|(\d[\d.]*)\ ?руб/p;
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