use strict;
my $str = 'john jane
john 123
john jim jane
jane john
jane 123
jane 456
jim
jim 1';
my $regex = qr/^(\S++).*\K(?:\R\1(?:\h.*|$))+/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