Why are we even bothing to check for the pipes? the solution, given the data provided, is as simple as:
#!/usr/bin/perl -w
use strict;

my $str = "|90|93|foo|bar|91|92|95|96|906|";

$str =~ s/9([0-9]+)?/x/g;

print "$str \n";

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In reply to Re: Replacing consecutive tokens in 1 pass by Anonymous Monk
in thread Replacing consecutive tokens in 1 pass by aarestad

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