use strict;
my $str = '_pranay_:pranay:104.144.219.145:3128
_ridhoo:rihdonk:104.144.224.242:3128
_shintna_10:shinhana:104.144.235.149:3128
_waled_jr_:ismail:104.144.241.222:3128';
my $regex = qr/^[^:\r\n]*:[^:\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