$Easting{$Line}{$Station}

That implies you intend to have 3 hashes, one for each of x, y & z. Parallel data structures are not (generally) a good idea as they can get out of sync and you're stuffed. Going by the line diagram, you'd be better off with something that allowed you to do:

my %line = (
    lineNameA => { 
        StationA => [ xxx.xx, yyy.yy, zzz.zz ],
        StationB => [ xxx.xx, yyy.yy, zzz.zz ],
        ...
    },
    lineNameB => { 
        ...        
);

my( $x, $y, $z ) = $line{ $lineName }{ $stationName };

# Or
use constant{ X => 0, Y => 1, Z => 2 };

my $y = $line[ $lineNo ][ $staionNo ][ Y ];
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That's assuming the the identifiers are names not numbers.

If they are numbers, or names of the form "line_003" and "station_12", (low, mostly sequential number postfixes ),

then you'd save some memory and be a tad quicker to use arrays instead of hashes:

my @line = (
    [  ## $line[ 0 ]
        [ xxx.xxx, yyy.yyy, zzz.zzz ], ## $line[0][0] (station 0)
        [ xxx.xxx, yyy.yyy, zzz.zzz ], ## (station 1)
        [ xxx.xxx, yyy.yyy, zzz.zzz ],
        ...
    ],
    [   ## Line[ 1 ]
        [ xxx.xxx, yyy.yyy, zzz.zzz ], ## Line[ 1 ][ 0 ]
        [ xxx.xxx, yyy.yyy, zzz.zzz ],
        [ xxx.xxx, yyy.yyy, zzz.zzz ],
        ...
    ],
    ...
);

my( $x, $y, $z ) = $line[ $lineNo ][ $stationNo ];

# Or
use constant{ X => 0, Y => 1, Z => 2 };

my $y = $line[ $lineNo ][ $staionNo ][ Y ];
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