#!/usr/bin/perl

use strict;
use warnings;

my %lookup;

for (<DATA>) {
  chomp;
  my ($k, $v) = split(/ -- /);
  $lookup{$k} = $v;
}

while(<>) {
  s/^(\w+)\b/$lookup{$1} || $1/e;
  print;
}

_ _DATA_ _
uidf2920 -- Schulz
uid60124 -- Maier
uidg1626 -- Muster
uidg1067 -- Mueller