Assuming a character set with a single-character-to-byte mapping: 

>perl -wMstrict -le
"use List::Util qw(reduce);
 ;;
 my @ra = qw(ABCDxyz  ABCfoo  ABCDEbar);
 ;;
 use vars qw($a $b);
 my $min_start_seq =
   reduce { length($a) < length($b) ? $a : $b }
   map m{ \A \x00* }xmsg,
   map $ra[0] ^ $_,
   @ra
   ;
 my $common_starting_substring = $ra[0] & ~$min_start_seq;
 print qq{'$common_starting_substring'};
"
'ABC'

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In reply to Re: Find the common beginning substring in an array of strings by AnomalousMonk
in thread Find the common beginning substring in an array of strings by technojosh

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