Just change what you put into @solutions. Replace

$i-$l+1
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with

# Start of match in first string
# End of match in first string
[ $i-$l+1, $i+1 ]
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or

# Start of match in first string
# End of match in first string
# Start of match in second string
# End of match in second string
[ $i-$l+1, $i+1, $j-$l+1, $j+1 ]
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or

# Start of match in first string
# Start of match in second string
# Length of match
[ $i-$l+1, $j-$l+1, $l ]
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and remove

map { substr($s, $_, $best_l) }
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