Even with 36 cases, I still see nothing like the 5 second difference you apparently are:

#! perl -slw
use strict;
use Time::HiRes qw[ time ];

sub test1 {
    my $a = $_[0];

#   return;
    if ($a==1) {}
    elsif ($a==2) {}
    elsif ($a==3) {}
    elsif ($a==4) {}
    elsif ($a==5) {}
    elsif ($a==6) {}
    elsif ($a==7) {}
    elsif ($a==8) {}
    elsif ($a==9) {}
    elsif ($a==10) {}
    elsif ($a==11) {}
    elsif ($a==12) {}
    elsif ($a==13) {}
    elsif ($a==14) {}
    elsif ($a==15) {}
    elsif ($a==16) {}
    elsif ($a==17) {}
    elsif ($a==18) {}
    elsif ($a==19) {}
    elsif ($a==20) {}
    elsif ($a==21) {}
    elsif ($a==22) {}
    elsif ($a==23) {}
    elsif ($a==24) {}
    elsif ($a==25) {}
    elsif ($a==26) {}
    elsif ($a==27) {}
    elsif ($a==28) {}
    elsif ($a==29) {}
    elsif ($a==30) {}
    elsif ($a==31) {}
    elsif ($a==32) {}
    elsif ($a==33) {}
    elsif ($a==34) {}
    elsif ($a==35) {}
    elsif ($a==36) {}
}

sub test2 {
    my $a = $_[0];

    return ;
    if ($a==1) {}
    elsif ($a==2) {}
    elsif ($a==3) {}
    elsif ($a==4) {}
    elsif ($a==5) {}
    elsif ($a==6) {}
    elsif ($a==7) {}
    elsif ($a==8) {}
    elsif ($a==9) {}
    elsif ($a==10) {}
    elsif ($a==11) {}
    elsif ($a==12) {}
    elsif ($a==13) {}
    elsif ($a==14) {}
    elsif ($a==15) {}
    elsif ($a==16) {}
    elsif ($a==17) {}
    elsif ($a==18) {}
    elsif ($a==19) {}
    elsif ($a==20) {}
    elsif ($a==21) {}
    elsif ($a==22) {}
    elsif ($a==23) {}
    elsif ($a==24) {}
    elsif ($a==25) {}
    elsif ($a==26) {}
    elsif ($a==27) {}
    elsif ($a==28) {}
    elsif ($a==29) {}
    elsif ($a==30) {}
    elsif ($a==31) {}
    elsif ($a==32) {}
    elsif ($a==33) {}
    elsif ($a==34) {}
    elsif ($a==35) {}
    elsif ($a==36) {}
}

sub test3 {
    return if $_[0] > 9;
    my $a = $_[0];

    if ($a==1) {}
    elsif ($a==2) {}
    elsif ($a==3) {}
    elsif ($a==4) {}
    elsif ($a==5) {}
    elsif ($a==6) {}
    elsif ($a==7) {}
    elsif ($a==8) {}
    elsif ($a==9) {}
    elsif ($a==10) {}
    elsif ($a==11) {}
    elsif ($a==12) {}
    elsif ($a==13) {}
    elsif ($a==14) {}
    elsif ($a==15) {}
    elsif ($a==16) {}
    elsif ($a==17) {}
    elsif ($a==18) {}
    elsif ($a==19) {}
    elsif ($a==20) {}
    elsif ($a==21) {}
    elsif ($a==22) {}
    elsif ($a==23) {}
    elsif ($a==24) {}
    elsif ($a==25) {}
    elsif ($a==26) {}
    elsif ($a==27) {}
    elsif ($a==28) {}
    elsif ($a==29) {}
    elsif ($a==30) {}
    elsif ($a==31) {}
    elsif ($a==32) {}
    elsif ($a==33) {}
    elsif ($a==34) {}
    elsif ($a==35) {}
    elsif ($a==36) {}
}

my @dispatch = (
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
    sub {},
);

sub test4 {
    return if $_[0] > 9;
    $dispatch[ $_[0] ]->( $_[0] );
}

my $start = time;
test1( $_ ) for 1 .. 1e6;
printf "test1 took: %.5f seconds\n", time - $start;

$start = time;
test2( $_ ) for 1 .. 1e6;
printf "test2 took: %.5f seconds\n", time - $start;

$start = time;
test3( $_ ) for 1 .. 1e6;
printf "test3 took: %.5f seconds\n", time - $start;

$start = time;
test4( $_ ) for 1 .. 1e6;
printf "test4 took: %.5f seconds\n", time - $start;

__END__
C:\test>junk37
test1 took: 1.70500 seconds
test2 took: 0.30789 seconds
test3 took: 0.29240 seconds
test4 took: 0.29207 seconds
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