my $type = event_hasher(\@event);

sub event_hasher {
    my $cur_event = shift;
    my %event_hash;
    for my $item (@$cur_event) {
        $item =~ s/://g;
        my ($key,$value) = split / /, $item;
        $event_hash{$key} = $value;
    }
    return \%event_hash;
}

$queue_changes{$event_id} = $type;
[download]

Update:
As choroba points out below this doesn't solve the problem - in fact it creates it! You need to make a copy of the input - but you are doing that anyway so the aliasing is not the problem. Using choroba's test with your subroutine:

sub event_hasher {
    my @cur_event = @{$_[0]};
    my %event_hash;
    foreach(@cur_event){
        $_ =~ s/://g;
        my @place_holder = split / /, $_;
        $event_hash{$place_holder[0]} = $place_holder[1];
    }
    return %event_hash;
}

my @event = ('a:b c:d');
print "@event\n";
my %type = event_hasher(\@event);
print "@event\n";

# prints:
a:b c:d
a:b c:d
[download]

The problem remains: $item is still an alias to the members of the @event.

#!/usr/bin/perl
use warnings;
use strict;

sub event_hasher {
    my $cur_event = shift;
    my %event_hash;
    for my $item (@$cur_event) {
        $item =~ s/://g;
        my ($key, $value) = split / /, $item;
        $event_hash{$key} = $value;
    }
    return \%event_hash
}

my @event = ('a:b c:d');
print "@event\n";
my $type = event_hasher(\@event);
print "@event\n";
[download]

($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]