join($column[2],$column[4])

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Is probably not doing what you think it is doing.

join EXPR,LIST

    Joins the separate strings of LIST into a single string with fields separated by the value of EXPR, and returns that new string

In your case, LIST is a single item, so the result of the join will be just $column[4].

You probably wanted: 

$motherID = "$column[2]$column[4]" # Interpolation
# OR (They both do the same thing)
$motherID = $column[2] . $column[4]; # Concatenation

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                Memory fault   --   brain fried

In reply to Re: How to map data from one column based on another column in perl by NetWallah
in thread How to map data from one column based on another column in perl by waekit

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