You know, I wish that I were a better programmer, so that I could be more succinct, but since Perl is very new to me, I do the best that I can, and try and learn from you folks. To answer your questions: @ARGV is set on the command line using the following syntax:

merge.pl file_1 a,b,c file_2 d,e,f
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where "a,"b",c" and "d,"e",f" are column headers. Columns are defined in the files as such:

#DFD ' '
#H Period Interface SrcRouter Subset MbitsCap Polls MbpsIn 
MbpsOut MbpsSum InMinUtil In5pUtil InAvgUtil In95pUtil InMaxUtil 
InUtilSD InMaxTS OutMinUtil Out5pUtil OutAvgUtil Out95pUtil 
OutMaxUtil OutUtilSD OutMaxTS EffMinUtil Eff5pUtil EffAvgUtil 
Eff95pUtil EffMaxUtil EffUtilSD EffMaxTS Class InPctDiscards 
InPctErrors InPctDiscErr InPctDiscErr95Q OutPctDiscards 
OutPctErrors OutPctDiscErr OutPctDiscErr95Q SecSysUpTime 
InWrapEvts InWrapCnts OutWrapEvts OutWrapCnts PctPollsGT80pUtil 
PctPollsGT1pDiscErr Flags KppsIn KppsOut IfDescr IfIndex
#F %-17s %-35s %-15s %-6s %9.5f %7d %14.3f %14.3f %14.3f %7.3f 
%7.3f %7.3f %7.3f %7.3f %9.5f %14s %7.3f %7.3f %7.3f %7.3f %7.3f 
%9.5f %14s %7.3f %7.3f %7.3f %7.3f %7.3f %9.5f %14s %3s %7.3f 
%7.3f %7.3f %7.3f %7.3f %7.3f %7.3f %7.3f %10d %7d %7d %7d %7d 
%7.3f %7.3f %-10s %14.3f %14.3f %-30s %-10s
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Specifically, what I want to do is: From file_1:

create a hash whose keys are any of the headers specified on the 
command line. Each key value is a reference to an array containing 
the data from each column.
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From file_2:

create another hash whose keys are any of the headers specified 
on the command line. Each key value is a reference to an array 
containing the data from each column.
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NOTE: There will ALWAYS be matching data between both files, but NOT necessarily under the same header label! For example:

the column "SrcRtr" from file_1 contains the exact same data as the 
column "DstDev" in file_2
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After assembling these data structures, I want to merge them, in structured format, and print the resulting merged file to <STDOUT>. I'm not sure if this is any clearer, but please let me know if it's not.