It seems as the delimiters were deleted, but the print is a little tricky

First, you had the string:

my $line = "a whole lotta shakin >pattern here< goin on";
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and you did

my @bits_and_pieces = split /></, $line;
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What did it make?
This code "splits" the string, searching '><' as delimiter. Because of '><' is not matched in the string, in @bits_and_pieces you will have only one element, and it would be

'a whole lotta shakin >pattern here< goin on'
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(all the string)

In the other hand, you did this

my $line = "a whole lotta shakin ><pattern here>< goin on"; 
my @bits_and_pieces = split /></, $line;
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Then, perl searches '><' in the string and splits it into an array.
So @bits_and_pieces would be now

('a whole lotta shakin ','pattern here',' goin on')
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If you print @bits_and_pieces with

print @bits_and_pieces;
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is printed

'a whole lotta shakin pattern here goin on'
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as if the delimiters '><' where removed from the array.

Hope this help
Hopes