I'm glad Ovid (++) mentioned the Deparse module, but be aware that different options can affect the output:

# no options:

$ perl -MO=Deparse -e 'my @lexlist = @_ or sort keys %lexicon'
sort keys %lexicon unless my(@lexlist) = @_;

#---
# using -x7 (level 7 expands code into equivelant logical constructs
# using &&, ?:, and do{}) -- (giving us back nearly the original)

$ perl -MO=Deparse,-x7 -e 'my @lexlist = @_ or sort keys %lexicon'
my(@lexlist) = @_ or sort keys %lexicon;


#---
# however, using -p (to fully parenthesize) can often help expose
# such problems as well:

$ perl -MO=Deparse,-p -e 'my @lexlist = @_ or sort keys %lexicon'
((my(@lexlist) = @_) or sort(keys(%lexicon)));
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It is sometimes useful to explore the output of Deparse with various options applied.