#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use XML::LibXML::Reader;

my $file = shift;

my $reader = 'XML::LibXML::Reader'->new(location => $file)
    or die "Cannot read $file.\n";
while ($reader->nextElement('signal')) {
    say $reader->getAttribute('id')
        if '3464' eq $reader->getAttribute('sigid');
}
[download]

Similarly, in XML::XSH2, a wrapper around XML::LibXML :

stream :N :f file.xml select signal[@sigid=3464] { echo @id }
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($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
[download]