You use a good technique for setting $alldata{'EXPRESS'}, splitting on a field delimiter inside array ref brackets:

$alldata{$key} = [split /;/, $value]
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You can place a SEQUENCE or PROTSYM element in a hash reference the same way:

# replaces everything in the last elsif(){...}
push @{$alldata{$key}}, {split /;|=/, $value};
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This works because a list with an even number of elements can always be treated as a hash. If you want to trim whitespace or something, that can be map'ped inside the braces.

After Compline,
Zaxo