Heres another way to do it, which seems more legible: 
use strict;
use warnings;

while (<DATA>){
    chomp;
    my @line = split /:/;
    print "$line[0]:$line[1]00:$line[2]:$line[3]:$line[4]00\n";
}

__DATA__
o:200806050852:b7199767:b24211012077030:200902232359
o:201103251457:b6235734:b2421100997663:201204022359
o:201403101021:b8015840:b24211013181843:201404072359
o:201407291225:b8759124:b24211001018862:201408262359

[download]
Output: 
o:20080605085200:b7199767:b24211012077030:20090223235900
o:20110325145700:b6235734:b2421100997663:20120402235900
o:20140310102100:b8015840:b24211013181843:20140407235900
o:20140729122500:b8759124:b24211001018862:20140826235900

[download]

In reply to Re^3: String concatenation issues with 00? by james28909
in thread String concatenation issues with 00? by bobdabuilda

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