Weird problem with PERL hashes on FreeBSD 10.3 that does not occur on RHEL7.2

[Crew]

Hi,

An issue has turned up, seemingly with PERL hashes on FreeBSD 
10.3-STABLE and 10.3-RELEASE-p21.

It involves a PERL script called EasyTimeline.pl. I have a simple 
reproducer that involves running EasyTimeline.pl with some input data 
(but you also need ploticus installed.)

When run on those two versions of FreeBSD the script will fail something 
like one out of five to seven times, but on RHEL it will never fail. On 
FreeBSD it will often fail the first time it is run, and then will 
succeed for the next five or so attempts and then fail again.

It seems to relate to one key in a hash being a proper prefix of the 
other and the order in which the keys are in the hash. In this case the 
keys are "grid" and "gridcolor".

I can supply the reproducer.

Does anyone have any ideas what might be causing this?

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