Bug in creating purchase order

[Nigel Titley <..hidden..>]

Go to Order Entry -> Purchase Order
Enter a creditor
Enter a partial description of an item and <return> or "update"

Internal server error

Error log says

Math::BigInt: couldn't load specified math lib(s), fallback to 
Math::BigInt::FastCalc at LedgerSMB/Form.pm line 61
Undefined subroutine &main:: called at bin/oe.pl line 1075.
Compilation failed in require at /usr/local/ledgersmb/oe.pl line 7.
[Fri Jul 13 17:43:35 2012] [error] [client 212.135.9.6] Premature end of 
script headers: oe.pl, referer: http://wol.homechip.com/ledgersmb/vendor.pl