#!/usr/bin/perl

print join(':', split(//, 'abc',  1)), "\n";    # => abc
print join(':', split(//, 'abc',  2)), "\n";    # => a:bc
print join(':', split(//, 'abc',  3)), "\n";    # => a:b:c
print join(':', split(//, 'abc',  4)), "\n";    # => a:b:c:
print join(':', split(//, 'abc', 99)), "\n";    # => a:b:c: