I'm too lazy too check¹ it, but it seems obvious that you shouldn't use int (which operates on native types¹) with Math::BigFloat objects.

from the docs:

CAVEATS

Do not try to be clever to insert some operations in between switching
+ libraries:
...
This will create objects with numbers stored in two different backend 
+libraries, and VERY BAD THINGS will happen when you use these togethe
+r:
[download]

so maybe better use ->bfloor() instead of int !?! :)

update

¹) but curiosity killed my cat: ;-)

code

#!/usr/bin/perl -w
use strict;
use Math::BigFloat ':constant';
use Data::Dump qw/pp/;

print "150 / 0.75 == ", 150 / 0.75, "\n";
print "150.5->bfloor() == ", 150.5->bfloor() / 0.75, "\n";
print "150 / 3.75 == ", 150 / 3.75, "\n";
print "150.5->bfloor() / 3.75 == ", 150.5->bfloor() / 3.75, "\n";

my $float=3.1415926;
pp $float;
pp $float->bfloor();
pp int($float);
[download]

output

150 / 0.75 == 200
150.5->bfloor() == 200
150 / 3.75 == 40
150.5->bfloor() / 3.75 == 40
bless({ _e => [7], _es => "-", _m => [1415926, 3], sign => "+" }, "Mat
+h::BigFloat")
bless({ _e => [0], _es => "+", _m => [3], sign => "+" }, "Math::BigFlo
+at")
bless({ sign => "+", value => [3] }, "Math::BigInt")
[download]

Please note that int produces an object of type Math::BigInt which was never used !!!

Not sure if Math::BigFloat should better try to overwrite CORE::int() differently...

footnote

¹) nope it's overwritten, see update and following discussion.