Assuming it is not a typo, you have several problems in this loop. I will start at the top and move down. 
foreach @line ( @data )

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I am not sure if this is a typo. What we refer to as "an array of arrays" is really an array of references. In this case, I think you meant: 
foreach $line ( @data )

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This of course will make changes into the 'if' clause, but you have some existing problems in there already. 

if ( @line[0] ...

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does not do what you think. You are referencing an array slice consisting solely of the first element in @line. Perl will DWYM and give you the referenced element of the array. Using -w would have caught this "mistake".

Again, assuming it isn't a typo, you want to say 

if ( $line[0]...

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in the generic case. In this case, though, since we have changed @line to $line ( ie, from an array to an array ref ), it really should look like 
if ( $$line[0]...

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or ( and this is my preferred form ) 
if ( $line->[0] == $tree ... )

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Of course, you will need to substitute this change through the entire line, ie, 
s/\@line/$line->/g;

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Finally, the last assignment probably needs to look like 

$mdarray[$tree][$stem][$height] = $line;

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This will stash the current array reference into the right location for later use.

All in all, I would highly recommend reading through perldsc ( the perl data structures cookbook ). I found it very useful when I was first learning how to handle perl's data structures. I would also recommend always developing with -w and use strict :)

mikfire

In reply to Re: Fail to see referencing problem to arrays (in an array of arrays) by mikfire
in thread Fail to see referencing problem to arrays (in an array of arrays) by Elias

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