In both cases you have an array and print does not insert any extra characters between the elements of an array. You can use join to do that however:

use strict;

my @days;
@days = qw(Monday Tuesday Wednesday Thursday Friday Saturday Sunday);
print ((join ' ', @days), "\n");

print join ' ', qw(Monday Tuesday Wednesday Thursday Friday), "\n";
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Prints:

Monday Tuesday Wednesday Thursday Friday Saturday Sunday
Monday Tuesday Wednesday Thursday Friday
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To see why I put the brackets in try these two lines:

print ((join ' ', @days), "x\n");
print join ' ', @days, "x\n";

#prints:
Monday Tuesday Wednesday Thursday Friday Saturday Sundayx
Monday Tuesday Wednesday Thursday Friday Saturday Sunday x
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Note the space before the x in the second line because @days, "x\n" is a list that join acts on, rather than the paraneter for join followed by a parameter for print.