Here is one way, using tr and substr (without using regular expressions): 
use warnings;
use strict;

while (<DATA>) {
    tr/-abcdef/9012345/;
    print substr($_, 0, 10);
    print "\n";
}

__DATA__
a81f9284-b353-430a-a8ce-85b8118d3f3e

[download]
See also (documentation available at your command line via perldoc):

To grab the output of an external command, such as uuidgen, you should use qx instead of system.

In reply to Re: Help in building Regular expression by toolic
in thread Help in building Regular expression by begin_101

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