If you find Zaxo's solution imaginative but complex and are put off by the sight of sauoq's daunting collection of brackets, comma's and star's that are so difficult to understand as well as get right, you might like to try:

Start with your example string

    10:03pm up 3 days, 9:27, 1 user, load average: 0.00, 0.00, 0.00
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Put brackets around the bits you want to capture:

    (10:03pm) (up 3 days, 9:27), (1 user), (load average: 0.00, 0.00, 
+0.00)
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Anchor the ends: (not always strictly necessary, but it usually doesn't hurt).

    ^(10:03pm) (up 3 days, 9:27), (1 user), (load average: 0.00, 0.00,
+ 0.00)$
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Substitute the minimum necessary for the bits that change:

    ^(.+?m) (up .+? days, .+?:.+?), (.+? user), (load average: .*?)$
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Deal with possible plurals: (Note: the s on users)

    ^(.+?m) (up .+? days?, .+?:.+?), (.+? users?), (load average: .*?)
+$
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Wrap in delimiters, bind and assign to the variables of your choice:

    ($Time, $Uptime $Current_Users,$CPU_Load) = 

    `/usr/bin/uptime` =~ /^(.+?m) (up .+? days?, .+?:.+?), (.+? users?
+), (load average: .*?)$/;
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Used on your sample input it renders:

    ($Time, $Uptime, $Current_Users,$CPU_Load) = 

        '10:03pm up 3 days, 9:27, 1 user, load average: 0.00, 0.00, 0.
+00' =~ 

            /^(.+?m) (up .+? days?, .+?:.+?), (.+? users?), (load aver
+age: .*?)$/;
    
    print '[', $Time, '] [', $Uptime, '] [', $Current_Users, '] [', $C
+PU_Load, ']';
    # Ouput
    [10:03pm] [up 3 days, 9:27] [1 user] [load average: 0.00, 0.00, 0.
+00]
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Possibly not as good as the other solutions, but arguably easier to modify if you wanted to adjust it yourself.

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What's this about a "crooked mitre"? I'm good at woodwork!