my %to_find = map { $_ => 1 } keys %{ $KLARF_REGEXP{$KLARF_VERSION} };

while ( <FILE> ){
    for my $field ( keys %to_find ) {
        next if !/$KLARF_REGEXP{$KLARF_VERSION}{$field}/;

        if ( @- > 1 ) {
            $summary->{$field} = $1;
            LogMsg( "Found $field $summary->{$field}" );
        } else {
            LogMsg( "Found $field" );
        }

        delete $to_find{$field};
    }
}

die if keys %to_find;
[download]

You'll get a slow down since you now have to check every pattern for every line instead of just one.

An alternative implementation is to load the entire file into memory if it fits.

my $file; { local $/; $file = <FILE>; }

for my $field ( keys %{ $KLARF_REGEXP{$KLARF_VERSION} ) {
    die if !/$KLARF_REGEXP{$KLARF_VERSION}{$field}/;

    if ( @- > 1 ) {
        $summary->{$field} = $1;
        LogMsg( "Found $field $summary->{$field}" );
    } else {
        LogMsg( "Found $field" );
    }
}
[download]