What have you tried?

perlrequick

This will capture.

if( $string =~ m/(?<!\d)(\d{4,5})(?!\d)/ ) {
  print "$1\n";
}
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If you want to capture all occurrences:

my( @found ) = $string =~ m/(?<!\d)(\d{4,5})(?!\d)/g;
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And if "strip" means remove:

$string =~ s/(?<!\d)\d{4,5}(?!\d)//g;
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