use 5.010;

say fraction_for_decimal($_)
	for qw( 0.3456 1.251 -0.1 -0.25 );

sub fraction_for_decimal
{
	my $decimal = shift;
	my $mult    = 10 ** length [ split m{[.]}, $decimal ]->[1];
	my ($num, $den) = (int($decimal * $mult), $mult);
	my $hcf = _hcf($num, $den);
	$_ /= $hcf for ($num, $den);
	return "$num/$den";
}

# Stolen from Number::Fraction.
sub _hcf {
	my ($x, $y) = @_;
	($x, $y) = ($y, $x) if $y > $x;
	return $x if $x == $y;
	while ($y) {
		($x, $y) = ($y, $x % $y);
	}
	return abs($x);  # changed this
}

__END__
216/625
1251/1000
-1/10
-1/4