use strict;
my $str = '01 - 10
This is the first one :1
02:45
This is the second one -2
03-88
This is the third one "3
04:40
This is the forth one ;4
05 - 50
This is the fifth one .5';
my $regex = qr/^(?!\d{2}\h*[:-]\h*\d{2}\h*$).*[\r\n]+/mp;
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